[Luke gestured down at the trough Toph had rather expertly carved out before. Specifically at a slot in the stone at the mouth of the new canal.]

Basically? I need you to slide the gate into that hole there while I hold back the water. Nothing too complicated, but with the barrier interfering with the Force I can't manage all of that by myself.

[Which wasn't technically true, it'd just be a lot more taxing on him than having help.]